Piping systems for high pressure and temperature fluids are generally designed to provide some degree of flexibility to allow for dimensional tolerances, thermal expansion and contraction, and vibrational deflections between the various components which are connected by the piping. Lightweight compact assemblies, which are particularly desirable in aircraft and missile systems, for providing such flexibility are known in the prior art; however, these prior art devices generally employ elastomeric, plastic, rubber or asbestos type seals to prevent leakage of the fluid flowing in the flexible system. A shortcoming of these types of seals is that they tend to fail when exposed to high temperatures above approximately 400.degree. F.-500.degree. F., very low temperatures, or radiation.
Typically, sealing assemblies used in flexible piping systems in environments beyond the capability of seals made of elastomers and the like employ sections of piping with circumferential corrugations, i.e., bellows, expansion loops, or devices containing piston rings. However, these devices are generally very heavy, require large amounts of space, and are prone to failure and, therefore, leakage, due to fragility and wear. Moreover, these sealing systems often require exact tolerances and are difficult to manufacture and install.
Solving these problems, it is known to utilize metal to metal seals in such an environment as disclosed in prior U.S. Pat. Nos. 4,054,306; 4,071,268 and 4,071,269, issued to the inventors herein. At higher temperatures, above for example 900.degree. F., the seals disclosed in these three patents perform extremely satisfactorily and leakage of fluid is minimal. This is because while a rubbing action of the two metallic parts, which are in sliding contact, tends to gall the contacting parts, an oxide film is continuously formed, maintaining a lubricious, non-galling surface. However, it has been noted that at more moderate temperatures this oxide film does not regenerate and thus galling tends to roughen the metallic surfaces, thereby increasing the chance of leakage of fluid between them.
In addition to maintaining the seal between joined pipes, it is important to provide a mechanism that allows for rotation and angulation between adjacent pipes. Typically, the prior art flexible joint devices include bellows-sealed gimbal, hook or ball joints, none of which combine the necessary capabilities in a light and compact arrangement.
Moreover, many of the prior art devices which allow for flexibility do not provide for a mechanism to limit relative rotation while allowing angular misalignment and they do not provide for a positive and reliable limit to angular misalignment.
Examples of such prior art devices are disclosed in the following U.S. Pat. Nos. 1,155,495 to Leake; 2,005,556 to Parker; 2,451,437 to Fenlon; 2,502,753 and 2,840,394 to Rohr; 2,846,242 to Drake; 3,033,595 to Bard; 3,165,339 to Faccou; 3,663,043 to Walton; 3,656,784 to Dow et al; 3,799,586 to Caras et al; 3,995,896 to Decker; 4,006,881 to Gaillard; and 4,165,107 to Affa et al.